The present invention relates in general to laser treatment of dermatological imperfections. The invention relates in particular to non-ablative laser treatment of hypotrophic scars and enlarged pores.
The aesthetic treatment of abnormal dermatological conditions such as scars and pores has hitherto involved primarily the removal of tissue and subsequent wound healing to improve their appearance. Chemical peels, dermabrasion, and ablative laser skin resurfacing are used routinely for this purpose. However, all of these methods leave open wounds which must subsequently heal. Prior-art treatments and investigations of treatments have been concentrated primarily on raised, keloid, or hypertrophic scars. Treatment of dermatological imperfections such as hypotrophic or depressed scars, such as those that are a common residual feature following acne treatment, has received relatively little investigative attention. While such imperfections may not be considered as aesthetically unpleasant or inconvenient compared with raised scars, which can often be discolored or crusted, they are nonetheless dermatological imperfections. There is need for a method of improving the character of these imperfections without causing damage to peripheral tissue, and without leaving an open wound which must subsequently heal
The present invention is directed to a method for treating any one or both of depressed scars or enlarged pores in human skin. In one aspect, the method of the present invention comprises irradiating the skin to be treated with light (electromagnetic radiation) having a wavelength selected such that it is preferentially absorbed in a dermal region of the skin including a melanocyte layer of the epidermis and a region of superficial vasculature immediately below the melanocyte layer. The light is delivered at a fluence sufficient that the preferential absorption thereof stimulates a wound healing response in the dermal region without causing a wound. The wound healing response promotes growth of dermal extracellular matrix (ECM) in the upper dermal region. The growth of dermal ECM reduces the depth of the depressed scars and reduces the size of the enlarged pores.
Preferably, the light has a wavelength between about 525 and 550 nanometers (nm). The light may be delivered in the form of pulses thereof or as a continuous beam swept or scanned over an area of skin being treated.
In experimental treatments in accordance with the present invention, pulsed electromagnetic radiation having a wavelength of 532 nm, delivered by a frequency-doubled Nd:YAG laser was arranged to deliver a spot having a diameter of about 3 millimeters (mm). The pulse duration was about 2.0 milliseconds (ms). An average fluence of 7.5 Joules per square centimeter (J/cm2) was used to treat twenty-four volunteer patients having dermatological defects including depressed (hypotrophic) facial scars and enlarged pores. There was on average a 65% improvement in the appearance hypotrophic scars, and a 50% improvement in the appearance of enlarged pores.